Officially called Patch Tuesday is the second Tuesday of the month, and is the date that Microsoft released their patches for the month.
Many users, and small companies, have set their computer to automatically update. These computers will daily check for updates, and apply them as they are releases. Or not...
It appears that the shear volume of computers attempting to check for updates causes timeouts. Which, again apparently, the computer treats as there are no updates available.
Same Bat Time, Same Bat Place...
MS automated updates all default to the same time, and most people never change the defaults. So each time zone pounds on the MS update servers , basically, in unison.
This is understandable from a programming perspective, but this results in large numbers of computers set for automatic updates vulnerable after Patch Tuesday.
Wherever I find this issue I automatically manually run updates, and I have found this issue 3 and 4 days after Patch Tuesday.
Its the second Wednesday of the month do you know where your computer's patches are...